


Sibling Sharing

by Nitrobot



Category: Transformers: Robots in Disguise (2015)
Genre: Double Penetration in One Hole, Established Relationship, F/M, Pregnancy Kink, Threesome - F/M/M
Language: English
Status: Completed
Published: 2015-08-04
Updated: 2015-08-04
Packaged: 2018-04-12 21:50:26
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,151
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/4495971
Author URL: https://archiveofourown.org/users/Nitrobot/pseuds/Nitrobot
Summary: <blockquote class="userstuff">
              <p>They say sharing is caring, but Sideswipe isn't so sure about that when it comes to his girlfriend and his obnoxious twin.</p>
            </blockquote>





	Sibling Sharing

**Author's Note:**

  * For [Princesa](https://archiveofourown.org/users/Princesa/gifts).



> First place prize of my tumblr fic giveaway for Princesa, who asked for Sunny/Strongarm/Sides with breeding kink thrown in. 
> 
> Sunstreaker ends up on Earth cause... he ended up being a suspected Decepticon imprisoned on the Alchemor or something.

"I call dibs on her valve."

With those six words, Sideswipe was swiftly regretting ever answering his twin's commlink.

"Um, excuse me but who here one, is the official boyfriend and two, busted your aft out of a prison pod in the first place?"

Sunstreaker only rolled his optics and batted Sideswipe's accusatory digits away from his face. " _You_ can have her valve any time you want, therefore I should get it first."

Sideswipe was almost impressed by his twin's reasoning that he forgot to be angry for a few nanoklicks. "That wasn't part of the deal, you slagging-!" He stopped himself mid-rant, replacing the insult with a groan as he wiped a hand down his faceplate. "Let's... just ask her who _she'd_ rather have first." 

Sunstreaker mulled it over for a klick and shrugged in a casual agreement, while Sideswipe couldn't help thinking, _'If she'd like to get out of her quarters any time soon, that is...'_ Strongarm had been gone for what felt like a breem, insisting she "prepared herself" for them. Apparently interface involved more than just sliding your armour off where she was concerned. 

Almost as if he managed to summon her, Strongarm's door edged open and her helm popped around the corner of it. Sideswipe somehow stopped himself staring at the patches of exposed silver protoform below her neck cables. She glanced from one twin to the other. "I heard arguing."

Sideswipe copied her swift look over at Sunstreak, smug aft expression and all. He had no idea how thick the walls of Strongarm's room were, but even he knew two mechs squabbling over positions didn't help set a good mood. "Not arguing, really, just... discussing." 

Sunstreaker, on the other hand, was more than willing to lay the truth out. "Which of us is gonna be in your valve first?" Either his time in stasis had left a short in his logic circuits, or he was even more impatient for the promise of a long night's fragging than Sides was. 

Strongarm quirked an eyeridge, frowning in confusion. "Aren't you both going to?"

Her tone made the solution seem obvious enough that Sideswipe ended up with energon rushing to his faceplate as he rubbed at his helm. "Well... eventually, yeah, but-"

Something seem to hit Strongarm's own helm in a sudden realisation as her optics widened above a smile of understanding. "I never said you had to do me one at a time, boys."

Now it was Sideswipe's turn to figure out what she was say-

Oh.

_Oh._

Sunstreaker's processor seemed to work faster than his, from how he was almost about to jumped past Strongarm to get into her quarters (granted, he was planning that as soon as he saw her, even after Sideswipe had pointed out she was _very_ taken).

Strongarm flashed a smirk before letting the door open all the way, revealing only a glimpse of her quarters behind her naked body leaning against the doorframe. Sideswipe had seen her bared before, but the sight of her still sent a sucker punch of shockwaves through his spark. At least he wasn't drooling like Sunny.

"What you two _should_ be asking is if you'd rather be getting a view of my aft or my chestplates," Strongarm suggested, letting them ogle for a few nanoklicks before stepping backwards and leading them into her quarters.

"I got a better question," Sunny whispered as they followed her inside with a nudge in Sideswipe's chest. "Which of us is gonna knock her up first?"

And the regret just kept growing. "Sunny, I swear to Primus if you freak her out with that-"

"Oh, don't act like it doesn't turn you on as well, Sides," Sunny deflected. "I know what I heard in Academy with you and that one Seeker femme-"

He always had to keep bringing up the bunk-sharing incident, didn't he? Sideswipe shut him up with a hard nudge in his servo, turning his attention where it belonged- on Strongarm. As always, her quarters were pristine with hardly a dust speck on her row of datapads out of place. He was only interested in what was right in front of him; her berth, complete with clean blankets and herself stretching out deliciously on top of it. 

There was a click behind them as the door closed, and a very noticeable purr in Strongarm's voice.

"Remember my 'day off' only lasts for tonight, so... make the most of it." The 'day off' that released her from the rule of not fragging former prisoners, in this case, Sunstreaker. 

And since it was such a special day for him, Sunny got first choice of chestplates. Sideswipe didn't mind; Strongarm's aft made up for not seeing her faceplate. 

He slid his spike against her plating while waiting for his twin to get her lube flowing, using his digits to make some space in her valve. Light blue liquid soon coated them and swelled past her rim, signalling that she was ready for him. Sides' spike head barely made it past the ribbing of his brother's ones, but with some more digit help he soon eased himself inside. It was strange having another spike rubbing against his own but he could easily get used to it from how how she moaned; spinal strut arching, valve walls rippling around both of them and leaking lube down her thighs, driving them both mad with her slow groans and whispered begging.

"You have amazing chestplates, Strongarm..." Sideswipe couldn't see his brother's face past their girl's writhing body, but he clearly had it buried in them from how muffled his voice was. "You ever thought about sparklings?"

Oh, scrap. Sideswipe brought himself down to Strongarm's audios, still thrusting into her. "Ignore him, baby, he's got a thing for carrying."

Strongarm barely managed to speak past a high pitched moan, tilting her helm back to lie against Sides' shoulder. "Maybe I do as well."

Her whispered revelation made Sides pause his pounding even as his spike flared with a new rush of arousal. Strongarm gave a bitten-lipped smirk before letting herself collapse back on top of Sunstreaker, giving him an even closer view of her chestplates as they rubbed up against him.

"Thinking of getting me pregnant before Sides can?" she asked, not seeing the scandalised look on her rear-fragger's faceplate.

Sunstreaker surfaced from her chestplates with a grin, glancing up at Sides. "Well, it'd work on pissing him off..."

"You're damn right it would!" Sides protested, trying to get himself back into the rhythm of riding Strongarm. She helped with co-ordinated thrusts against him, coaxing him back into pleasure with another foreign, almost teasing smirk.

"Then I guess you better overload in me first, sweetspark."

It wasn't the kind of race Sideswipe was used to being in, but he'd still win it. He knew he wasn't ready to put up with whatever would spawn from his brother.


End file.
